Semiconductor device

Abstract

A power diode is disclosed wherein it is possible to lower on-voltage by expanding a conducting region at an on time. By applying negative voltage to a plate electrode when turning on a power diode, an inversion layer is formed in a front surface layer of an n drift region sandwiched between a p guard ring region and a p anode region, and the p guard ring region and p anode region are connected by the inversion layer, thereby causing one portion or all of the p guard ring region to function as an active region together with the anode region, and expanding an energization region, thus lowering on-voltage.

What is claimed is: 
     
       1. A semiconductor device, comprising:
 a first conductivity type semiconductor substrate; 
 a second conductivity type first semiconductor region that is disposed in a front surface layer of the first conductivity type semiconductor substrate; 
 a second conductivity type guard ring region that is a breakdown voltage structure disposed surrounding the first semiconductor region, the guard ring region including a plurality of guard rings; 
 an insulating film that extends from an end portion of the first semiconductor region and formed to continuously extend over the plurality of guard rings; 
 a conductive film that is disposed on the semiconductor substrate so as to be sandwiched between the end portion of the first semiconductor region and an end portion of the guard ring region, and on the guard ring region via the insulating film; and 
 a main electrode, disposed on the first semiconductor region, which is spaced away from the conductive film, 
 wherein the insulating film is formed between the second conductivity type guard ring region and the conductive film without a trench in the insulating film reaching the second conductivity type guard ring region, 
 wherein the guard rings are disposed relative to each other and the first semiconductor region so that
 an on-time voltage, which is applied to the conductive film at an on-time, forms inversion layers in the front surface layer of the semiconductor substrate, the inversion layers connecting the guard rings to the first semiconductor region, and further connecting the guard rings to each other, and 
 an off-time voltage, which is applied to the conductive film at an off-time, extinguishes the inversion layers. 
 
 
     
     
       2. The semiconductor device according to  claim 1 , wherein:
 the guard rings are second conductivity type second semiconductor regions each having a high concentration; 
 the conductive film is divided into ring shapes; and 
 the divided ring-shaped conductive films are disposed, via the insulating film, on a portion of the semiconductor substrate that is sandwiched between the first semiconductor region and the guard ring region and on another portion of the semiconductor substrate sandwiched between adjacent ones of the second semiconductor regions. 
 
     
     
       3. The semiconductor device according to  claim 2 , wherein one portion of the semiconductor substrate forms a Schottky barrier junction. 
     
     
       4. The semiconductor device according to  claim 1 , wherein one portion of the semiconductor substrate forms a Schottky barrier junction. 
     
     
       5. The semiconductor device according to  claim 1 , wherein:
 the first conductivity type semiconductor substrate is an n-type semiconductor substrate; 
 the second conductivity type first semiconductor region is a p-type anode region; 
 the second conductivity type guard ring region is a p-type guard ring region of high concentration; and 
 the conductive film is a plate electrode. 
 
     
     
       6. The semiconductor device according to  claim 1 , wherein the conductive film is free of any direct contact with the second conductivity type guard ring region. 
     
     
       7. The semiconductor device according to  claim 1 , wherein when the on-time voltage is applied to the conductive film at the on-time, a first of the inversion layers directly contacts both a first of the guard rings and the first semiconductor region, and a second of the inversion layers directly contacts both the first of the guard rings and a second of the guard rings. 
     
     
       8. A semiconductor device, comprising:
 a first conductivity type semiconductor substrate; 
 a second conductivity type first semiconductor region that is disposed in a front surface layer of the first conductivity type semiconductor substrate; 
 a second conductivity type guard ring region that is a breakdown voltage structure disposed surrounding the first semiconductor region, the guard ring region including a plurality of guard rings; 
 an insulating film that extends from an end portion of the first semiconductor region and formed to continuously extend over the plurality of guard rings; and 
 a conductive film that is disposed on the semiconductor substrate so as to be sandwiched between the end portion of the first semiconductor region and an end portion of the guard ring region, and on the guard ring region via the insulating film; 
 wherein the guard rings are a plurality of second conductivity type second semiconductor regions each having a high concentration; 
 wherein the conductive film is divided into ring shapes; and 
 wherein the divided ring-shaped conductive films are disposed, via the insulating film, on a portion of the semiconductor substrate that is sandwiched between the first semiconductor region and the guard ring region and on another portion of the semiconductor substrate sandwiched between adjacent ones of the second semiconductor regions, 
 wherein the insulating film is formed between the second conductivity type guard ring region and the conductive film without a trench in the insulating film reaching the second conductivity type guard ring region, 
 wherein the guard rings are disposed relative to each other and the first semiconductor region so that
 an on-time voltage, which is applied to the conductive film at an on-time, forms inversion layers in the front surface layer of the semiconductor substrate, the inversion layers connecting the guard rings to the first semiconductor region, and further connecting the guard rings to each other, and 
 an off-time voltage, which is applied to the conductive film at an off-time, extinguishes the inversion layers. 
 
 
     
     
       9. The semiconductor device according to  claim 8 , wherein the conductive film is free of any direct contact with the second conductivity type guard ring region. 
     
     
       10. The semiconductor device according to  claim 8 , wherein when the on-time voltage is applied to the conductive film at the on-time, a first of the inversion layers directly contacts both a first of the guard rings and the first semiconductor region, and a second of the inversion layers directly contacts both the first of the guard rings and a second of the guard rings.